Problem: Tiffany starts counting at 47, and she counts by threes. If 47 is the 1st number that Tiffany counts. what is the 15th number that she counts?
What is the first number that she counts? $47$ What is the second number that she counts? $\begin{align*}&47 + 3 \\ &= 50\end{align*}$ What is the third number that she counts? $\begin{align*}&47 + 3 + 3 \\ &= 47 + (2 \times 3) \\ &= 53\end{align*}$ What is the 15th number that she counts? $\begin{align*}&47 + (14\times3) \\ &= 47 + 42 \\ &= 89\end{align*}$